Refining of hydrocarbon oils



March 2, 1954 R. c. ARNOLD ET AL 2,671,046

- REFINING OF HYDROCARBON OILS Filed June 2l, 1951 A INVENTORS: ROBERT C. ARNOLD 'ARTHUR P. L l EN BY: @n

ATTORNEY:

BF?, STORAGE Patented Mar. 2, 1954 REFINING OF HYDROCARBON OILS Robert C. Arnold, Park Forest, Ill., and Arthur P. Lien, Highland, Intl.,l assignors to Standard Oil Company, Chicago, Ill., a corporation of Indiana Application June 21, 1951, Serial No. 232,822

14 Claims. (Cl. 196-14.19)

'I'his invention relates to the treatment of hydrocarbon oils which contain organic sulfur compounds and aromatic hydrocarbons. More particularly, the invention is directed to the treatment of petroleum oils boiling inl the heavierthan-gasoline range which contain aromatics and undesirable amounts of organic sulfur compounds. Still more particularly the invention relates to the removal of a separate fraction I of low-sulfur aromatics and a separate fraction of essentially organic sulfur compounds from hydrocarbon oils containing these compounds in addition to parainic and/or naphthenic compounds.

Practically all hydrocarbon oils derived from" natural sources consist of paraiiins, naphthenes, aromatics, organic-sulfur compounds and some organic nitrogen and oxygen compounds. For

some purposes the presence of aromatics is desiroil obtained from West Texas crude contains about 20 of aromatic compounds and about 4% of organic sulfur compounds, its total sulfur content being about 0.7%.

A very large number of processes for reducing sulfur and aromatic content have been developed,

such as, sulfuric acid treating, silica gel extraction, liquid SO2 extraction, etc. These processes either change the chemical nature of the compounds removed, or remove a mixture of aromatic and sulfur compounds which can be separated with difficulty or only at excessive cost. Recently a large demand has arisen for relatively pure organic sulfur compounds, of the type naturally occurring in petroleum oils, as starting materials for synthetic detergents, fungicides, ininsecticides, etc. At the same time there is great demand for aromatic concentrates and pure aromatic compounds particularly for use in polymerio materials, detergents, super solvency naphthas, etc.

An object of our invention is to refine hydrocarbon oils by substantially reducing the amount of organic sulfur compounds and aromatic compounds present therein. Another object is to produce a domestic fuel oil `of good burning quality and odor by removing organic sulfur compounds and aromatic compounds therefrom.

2 A particular object is to treat hydrocarbon oils containing organic sulfur compounds and aromatic compounds and recover therefrom a sep- Y arate fraction of essentially organic sulfur compounds and a separate fraction of essentially aromatic compounds.

We have discovered that a hydrocarbon oil containing aromatic compounds and organic sulfur compounds can be separated into a low sulfur and low aromatic content refined oil, an essentially aromatic hydrocarbon fraction and an essentially organic sulfur compound. fraction by a combination process comprising: contacting, in a first extraction step, the feed oil with liquid SO2 having dissolved therein aromatic compounds and a promoter which increases the organic-sulfur compound solution ability of the liquid SO2 and has little or no effect on aromatic solubility therein, and separating a low sulfur content rst raffinate phase from an essentially organic sulfur compound-liquid SO2-promoter extract phase; and, in a second extraction step, contacting the rst raiiinate with liquid SO2 under conditions rei sulting in the separation of a low sulfur, low aromatic content second rainate phase, and an essentially aromatic hydrocarbon-liquid SO2 extract phase, which extract phase can be, in part, used as the solvent in the first extraction step.

Liquid SO2 is elfective, at temperatures below about |10 C., in removing aromatic compounds from mixtures with paraffinic and naphthenic compounds particularly good results are obtained at temperatures below 0 C. However, liquid SO2 is not particularly effective in removing organic sulfur compounds. 'I'he sulfur-removing powers of liquid SO2 an be enhanced by adding a promoter, such as, liquid HF, sulfonic acids, etc. Promoters selected from the class of Friedel- Crafts type halides are remarkably effective in liquid SO2 at these low temperatures. Sufiicient liquid SO2 must be used to exceed the solubility of liquid SO2 in the oil so as to form a separate phase.

Not all the members of the class of compounds known as the Friedel-Crafts type halides can be used in our process. Some members are completely ineffective, for example, aluminum triv fluoride, or are only feebly effective, for example,

antimony trichloride, aluminum bromide amdv AlCls, FeCls, TiCh, BFa, HgClz, BCla, and ZnClz. Because of its solubility in liquid SO2, ease in recovery from the extract phase and excellent desulfurization obtained therewith, we prefer to use BF3. (The presence of Water is deleterious to the eiiicacy of the promoter and therefore we use substantially anhydrous material).

An appreciable amount of desulfurization, in excess of that resulting from the use of liquid SO2 alone, can be obtained by using as little as 0.5 gram mole or" promoter per gram atom of sulfur prsent in the raw oil undergoing treatment. Virtually complete desulfuriaation can be obtained by using up to about 5 moles of promoter. (It is to be understood that the term moles oi promoter when used in this speciiication and attached claims means gram moles of promoter per gram atom of sulfur present in the raw oil undergoing treatment.) 'I'he amount of promoter needed to obtain a certain pre-determined amount of desulfurizaticn will vary with the Volumes of liquid SO2 used in the treatment. However, in general, from about l to about 3 moles of promoter will give the desired result.

The amount of liquid SO2 used may vary from just enough to form two phases to 200 volume percent or more based on raw oil. It is of interest that less than the amount of liquid SO2 that is merely soluble in the oil can be used, as the presence of the promoter and associated sulfur compounds depresses the solubility of SO2 in 'the oil. For example, at 35 C., about 14% of SO2 is soluble in a virgin West Texas heater oil; when only of SO2 and l mole of AlClg are added to the oil at this temperature, two phases separate. At a iixed promoter usage, the extent of desulfurization increases markedly with increase in liquid SO2 usage up to about 25 volume percent of liquid SO2; above this point the gain in desulfurization is small per unit of liquid SC2 increase and about 100 volume percent appears to be about the practical maximum. In general we prefer to use from at least enough liquid SC2 to exceed the solubility of SO2 in the raw oil, and preferably about 25%, to about 100 volume percent of liquid SO2 based on raw oil.

In our combination process, in the second extraction step the liquid SO2 is removing essentially only aromatic compounds, so that larger quantities of liquid SO2 are preferred. In the extraction of the iirst raffinate, we prefer to use between about 50 and about 200 Volume percent of liquid SO2 based on rst raiiinate oil.

We have discovered that, `when liquid SO2- aromatic solution is used, in conjunction with a promoter, for the extraction of raw oil, not only is the extraction of aromatics suppressed somewhat but also the sulfur compounds dissolved into 'the liquid SO2-promoter solution force some of the dissolved aromatics out of the extract phase and into the raiiinate phase; thereby the extract phase from this first extraction step consists essentially of sulfur compounds, and the promoter dissolved in liquid SO2. We have found that this extraction should use an aromatic compoundliquid SO2 solvent in the smallest possible volume consistent with desulfurization in order to 0btain lowest aromatic content in the sulfur com pound fraction; and we prefer to use from about to about 50 volume percent of liquid SO2. present in theV solvent, based on raw oil. The greater the proportion of aromatics in the liquid SO2-aromatic solvent used in the extraction of the raw oil the greater will be the SO2 requirement in order to obtain two-phase separation.n

The eiectiveness of the liquid SO2-promoter solvent is substantially independent of temperature below about 0 C. Above 0 C., the desulfurization effectiveness of liquid SO2-promoter solvent decreases rapidly; +10 C. is about the highest temperature at which reasonable eiectiveness can be maintained. In addition to the eiect on desulfurization, the temperature of contacting has an eiect on the color of the final oil. At contacting temperatures of about -20 C. and below, final oils of excellent color (nearly water-whiteli are obtained. The color of the nal oil darkens markedly as the temperature of contactingincreases until at about 0 C., no improvementis obtained. Although the extraction steps in our combination process could be operated at different temperatures, we prefer to operate at the same temperature of below about |10 C.. and preferably between 0 C. and 40 C.

The time period required in our refining process will be dependent upon the intimacy of contacting with the solvent and also upon the contacting temperature. Ordinarily, the time period will be between 1/2y minute and about 60 minutes, and preferably about 5 minutes.

When the raw oil is very viscous or of relatively high pour point, it may be desirable to dilute the raw oil with a low boiling material such as butane, pentane, hexane, petroleum ether, etc., which is inactive toward the liquid SO2 and the promoter.

Our refining process can be used for various petroleum feed stocks, such as naphtha, kerosene, heater oil, gas oils, and lube oils. Also the process can be used on the oils from various conversion processes, for example, thermal cracking, coking, catalytic cracking, products of other solvent extraction processes, etc. While thermally cracked oils can be utilized in our process, the high olenn content interferes somewhat with the separation and the polymers formed contaminate the extract fractions. Catalytically cracked oils are particularly suitable feed for our process because they contain large amounts of sulfur compounds and aromatic compounds. Any hydrocarbon oil made up of a mixture of paraiiins, naphthenes, aromatics and organic sulfur compounds is a suitable feed for our process.

In some instances, the aromatic and organicsulfur compounds may be of more value than the reiined oil produced and the process may be operated even though more rened oil is made than is required. In such a case, the renned oil makes an excellent feed to a catalytic cracking process, since it is low in the two materials that are objectionable in catalytic cracking feed. The catalytic cracking operation builds up aromatics and refractory organic sulfur compounds;

RUNI

A virgin West Texas heater oil (obtained by distillation from a high sulfur West Texas crude) with the following` characteristics was treated with liquid SO2 and BFa.

API 40.9 Sulfur (wt. percent) 0.61 un 1.4558

Liquid SO2, 500 ml., was added to 500 ml. of the heater oil contained in a reactor provided with a cooling jacket and mechanical agitator. .The temperature of the reactor contents was maintained at 20 C. BF3, in the amount of 2 gram moles per gram atom of sulfur in the heater oil, was metered into the closed reactor. Atl this point a pressure of from 10 to 100 p. s. i. g-, due largely to BF3, existed in the reactor; this presn sure fell quickly to about p. s. i. g. when agitation was started. Agitation'was continued yfor minutes; the reactor contents were allowed to settle for 30 minutes before the raffinate phase and extract phase were withdrawn. The rafnate phase was washed with water, then with aqueous caustic, again with water, and then dried. This procedure removed all traces of the SO2 and BF; which were dissolved in the treated oil. The SO2 was dashed from the extract phase and the BFa complex decomposed by heating, followed by a caustic wash. The yield of rafiinate oil was 85 Volume percent; this treated oil had the following characteristics: sulfur, 0.086%; refractive index of nDZO, 1.4468; mercaptan number, doctor sweet. The extract oil had a sulfur content of 4.3%.

RUN II A sample of the heater oil described in Run I was treated in a series of batchwise steps in order to simulate equilibrium countercurrent contacting. Raw oil was treated with 100 volume percent of liquid SO2 at 20 C., the extract phase was used in conjunction with BF3 to treat more raw oil; the raiiinate from the extract phase-B55 solvent treat was then contacted with liquid SO2 alone.

Raw oil was contacted with 28 volume percent of extract phase, which contained 26 parts of liquid SO2 and 2 parts of aromatic compounds, and 2 mols of Bla per gram atom of sulfur in the raw oil at a temperature of 20 C. for 5 minutes. The rst rainate was separated from the rst extract phase; this rst raffinate was then contacted with 100 volume percent of liquid SO2 at 20 C. for 5 minutes; the second raffinate was separated and washed with caustic and water to remove dissolved SO2. The SO2 was removed from the second extract phase. A1- though an equilibrium equivalent to countercurrent contacting was not reached in this particular instance, the following results were obtained.

The treated oil (second raffinate) was obtained in 83.5 volume percent yield and had a sulfur content of 0.07 wt. percent; a refractive index of nnm, 1.4450; and an API gravity of 44.1. The rst extract oil, which was comprised substantially of organic-sulfur compounds, represented 7.0 volume percent of the raw oil and vhad a' RUN III In this run there was treated a light recycle catalytic gas oil obtained by distillation of the 6 product fromthe cracking of aimixture of various virgin gas oils at about 900 F. in the presence of a silica-alumina catalyst. This light cat gas oil had the following characteristics:

API 30.1 Sulfur (wt. percent) 1.34 n.320 y 1.4963

ASTM distillation: t v

IBP L F 415 50% F 460 Max. F 525 Liquid'SOz, 250 ml.,1was added to 250 m1, of the recycle oil contained in a reactor provided with a cooling jacket and vmechanical agitator. The

" temperature of the reactor contents was maintained at 20" C. by a Dry Ice acetone bath. AlCla, in the amount of 2 gram moles per gram atom of sulfur in the heater oil, was added into the reactor and the reactor closed. Agitation was continued for about 2 minutes. The mixture was allowed to settle and the two phases therein separately withdrawn. The raffinate phase was water and caustic washed to remove dissolved SO2 and AlCl3. The SO2 was flashed from the extraction phase and the AlCla-oil allowed to stand untilV it separated into an aromatic oil containing about 4% sulfur and an A1013 sludge. This sludge was hydrolyzed to yield a very high sulfur, viscous, tarry liquid with drying oil properties. The rafnate oil represented 65%of theraw oil, and had the following characteristics: sulfur, 0.18%, nD20, 1.4656. y

RUN IV A sample of the light cat cycle oil was treated in a manner-similar to Run II in order to simulate countercurrent contacting. In the first extraction step 64-volume percent, based on raw oil, of second extract phase which contained about 5l parts of liquid SOzand 13 parts of aromatic compounds, and 2 moles of A1Cl3 per gram atom of sulfur in the raw oil, were contacted at a temperature of 20 C. for 5 minutes. The treated oil (second rainate) had a sulfur content, 0.04%; nD2, 1.4505; and an API gravity, 43.1. The first extract oilhad a sulfur content 5.5%. The second extract oil had a sulfur content, 0.54% and a 711320, 1.5428. y

The above runs do not represent the equilibrium attainable in countercurrent operations and therefore do not give as good separationsas can be obtainable with the more eicient operation. They do illustrate this fact: Our process operating with no more of the solvent than the conventional single tower processes can produce a refined oil in the same yields and quality as the conventional process, a relatively low sulfur aromatic hydrocarbon fraction, and a fraction consisting substantially entirely of organic sulfur compounds. 1

In order to more fully describe a specific vernbodiment of our invention, reference is made to the accompanying drawing which constitutes a part of this specification and in which a schematic flow diagram of our process is shown.

The feed stock, for example, a virgin heater oil from a West Texas crude, is passed through line H into a drying zone I2 Awherein it is substantially dehydrated. The presence of water in th-e treating system is extremely undesirable because water combines with BFS to form hydrates, which hydrates complicate, the recovery of BFS; and the presence of water increases the corrosive tendenciesof the SO2 refining agent. kDrying zone I2 comprises conventional equipment such as, for example, a 'vessel packed with ealc'm chloride. alumina gel, or the like.

A'I'he dri-ed lraw oil is passed -through line i3 into deaeration equipment i4, wherein air dissolved or entrained in the feed oil is Vsubstantially removed. Conventional deaeration yequipment such as is ordinarily employed in` comercial processes of liquid SO2 refining of hydrocarbon oils may be employed. The dried deae'rated feed oil is passed through line I'6 into heat exchanger l1, wherein the temperature o1' the feed oil is lowered to the desired treating temperature.

In the vcase of very viscous hydrocarbon feed oils, the viscosity of the oil can be reduced by dilution with a paraiiinic hydrocarbon such as butane, pentane, petroleum ether, etc. The diluent may be introduced into line i6 through valved line 48.

The dried deaerated (diluted) feed oil is introduced into the lower portion of treating or extraction tower i9. The extraction tower may be packed with corrosion-resisting materials, or may be of modiiied bubble cap type construction. In tower I 9 the feed oil is contacted with B Fa and a solvent consisting of liquid SO2 that is substantially saturated with aromatic compounds derived from the particular feed oil being treated. vIf desired, the BF; and solvent may be combined and introduced into the upper portion of towerrg as one stream. AIn this type of operation BFa is withdrawn from storage drum 2i through line 22 and valved line 23, and is passed into line 24. Alternatively, solvent alone may be introduced through line 24 and BFa may be introduced into the extraction tower through line 22 and manifold 2t.

Contacting in extraction tower i9 may be effected at temperatures between about C. and

about 60 C., preferably at about 20 C. and i at pressures between 0 and about 100 p. s. i. g.; sunicient pressure inust be maintained on the system to keep the SO2 in the liquid state. The amount of liquid SO2 contained in the solvent introduced 'into tower I9 may be between about 15 and about "50 volume per cent based on the feed oil. It is desirable to keep the amount of liquid SO2 that is introduced into this rst extraction step as low as the 'desired degree of desulfurzation will permit. With large quantities of liquid SO2 the effectiveness of the BFs in selectively removing sulfur compounds to the exclusion of aromatics is lsomewhat impaired. Thus the smaller the volume o'f liquidSOz added to first extraction step, the smaller the amount of aromatic compounds carried vout of the system into the organic sulfur compound fraction product. Thuswe 'prefer to use such an amount of solvent that theainount of liquid `SO2 will be between about and 35 volume per cent and preferably be `about 25 volume per cent based on feed oil. v

The amount of BFa may be between about 0.5 and about 5 moles per 'gram atom of sulfur in the feed oil. Preferably, the amount of BF3 used should be between 1 and 3 moles.

The contacting period 4in tower I9 may be varied between about 1/2 and about 60 minutes and is preferably about 5 minutes.

The rst rainate is withdrawn from the upper part 'of tower I9 through line 21 and valved line 28 into stripping tower 29. v. Stripping tower 29 may contain packing`-material, bubble trays, or even be unpacked. order to maintain the proper temperature for removing dissolved IBFs remove the SO2 and SO2 from the nrst raiiinate, towery 23 is pro- `v-`1ded with 'a reb'oIer 3l. The stripped first rafnate is passed from stripper 29 .into cooler 32 and through valved line 33 and line 34 into extraction tower 36. Ordinarily it will not be neccessary to remove dissolved BF from the iirst raffinate as the amount of this material will be too slight to aiect treating in the second extraction step. However, to eliminate the possibility that excessive amounts of BF3 may be carried over into the second extraction step, stripping tower 29 has been provided; SO2 and BF3 pass out of stripper 29 by line 30. When stripper 29 is not being used the first rafnate may be by- .passed by means of valved line 31 into line 34 and thence into extraction tower 36. In extraction tower 35 the Vr'st raiin'at'e is contacted with liquid 'SO2 which is withdrawn from storage 38 and passed through line 39 into the upper portion of extraction tower 3B. The amount of liq'- uid `SO2 introduced into tower 36 may be between about .15 and about 200 volume per cent by volume of first raflinate, preferably between about 25 and volume per cent, while the temperature and pressure maintained in tower 35 may be different from that in tower I9. We prefer to operate the second extraction step at about the same temperature, Vi. e. about 20" C. and same pressure as that maintained inthe rst extraction step. lIhe second raffinate is withdrawn from tower St and passes through line 4I to stripper 42, which stripper is similar in construction to stripper 29. The temperature of the second raflinate oil is raised high enough by means of reboiler 43 to dissolved therein. The SO2 stripped from Vthe lsecond rainate passes out of the stripper 42 through line 40. The treated oil (SO2-free second rainate oil) passes out of stripper 42 by line l46 to storage or further treatment. The extract phase from tower '36 passes out of the tower through line 41; a suitable portion of the extract is passed through valved line 48 to line 24 for use as solvent in the first extraction step. That portion of the extract phase from tower 38 not needed for the nrst extraction step in tower I9 passes through valved line 4S into stripper 5I, which is vsimilar in construction to strippers 29 and 42. In stripper 5i the SC2 is removed from the extract oil by means of heat provided by reboiler 52. The SO2 passes out of stripper 5I through line 53 and the aromatic compound fraction passes from stripper 5l byline 54 to storage 'or further treatment.

The rst extract phase from tower i3 passes out of the tower through line 56 into stripper 5l' which may be similar Vin construction to strippers 29, 12, and 5L The rst extract phase may subjected Ato a sufficiently high temperature by means of reboiler 58 to vaporze substantially all the 4S92 and BFs present therein. Such temperatures fall within the range of about 50 C. to about 250 C. The SO2 and BFs free extract oil, consisting essentially of organic-sulfur compounds, is Withdrawn from stripper 5l through line 59 to storage or further treatment. The SO2 and BF pass overhead from stripper 5i through line 6 i.

From time to time, it may be necessary to send the SO2 or SO2--BF3 streams from the strippers to a dehydration operation for the removal of water which tends to .build up in the system. In such event, the streams in lines 30 and "it may pass through valved lines 61.?, 53 and 6ft; the stream from line 53 may pass through lines 63 and 64; andthe stream in line 6| may pass through line s4 to dehydrator ss. From dehydrator 66, the SO2, BFs and some HzS which forms during the high temperature dissociation of the BF2-sulfur compound complexes, pass through line Bl to a purification system 68. The streams from strippers 29, 42 and 5| may be passed directly to purification system 68 by way of lines 62 and 69.

The purification system v68 separates the SO2, BFa and I-IzS; fractional liquifaction may be used because of the spread between the boiling points of these compounds. From system 68, the BFs passes through line 1l, compressor 12 and cooler 73 to BFa storage 2|. Some losses are inevitable, so additional BFs may be added from source 74. From system $8, the SO2 passes by line 16, compresser l'l, and cooler 18 to SO2 storage 38 makeup SO2 may be added from source 19.

It should be understood that many details of process technique have been omitted in the above specific embodiment of our process. Common expedients which have been employed in commercial SO2 reiining processes will suggest themselves to those skilled in the art; such expedients are within the purview of the present invention.

The invention disclosed herein is an improvement on the inventions disclosed and claimed in our Iapplication No. 182,613, iiled August 31, 1950, and now abandoned, and in our application No. 201,174, filed December 16, 1950, now U. S. Patent 2,648,390.

We claim:

1. A process for rening a hydrocarbon oil which contains both aromatic and sulfur compounds, which process comprises extracting said oil in a iirst extraction zone with an aromatic compound-liquid SO2 solvent and an effective amount of an added promoter selected from the class of Friedel-Crafts halides consisting of BF3,

AlCla, FeCls, TiCl4, HgClz, B013 and ZnClz, and the amount of liquid SO2 being sufcient to eect formation of a separate phase in the presence of the oil and promoter whereby a nrst extract phase which contains liquid SO2, promoter and predominantly organic-sulfur compounds and a first raffinate phase are obtained, extracting said nrst raffinate phase in a second extraction zone with liquid SO2, in the absence of any substantial amount of said promoter, to obtain a second rainnate phase substantially reduced in both aromatic and organic-sulfur compound content and a second extract phase which contains liquid SO2, predominantly aromatic hydrocarbons and a minor amount of organic-sulfur compounds, removing SOz and promoter from said iirst and second extract phases respectively and removing SO2 from said second raiinate phase.

2. The process of claim 1 wherein the contacting in each of the extraction steps is effected at a temperature in the range of C. to 60 C.

3. The process of claim 1 wherein the amount of promoter used in said rst extraction zone is between about 0.5 and 5 gram moles per mole of sulfur in said oil.

4. The process of claim 1 wherein the amount of said solvent used in said rst extraction step contains from about to about 50 volume per cent of liquid SO2, based on said oil.

5. The process of claim l wherein the amount of liquid SO2 used in said second extraction zone is between about 15 and 200 volume per cent, based on said rst raii'inate oil.

6. The process of claim 1 wherein a part of the second extract phase with its contained SO2 is 10 employed to supply both liquid SO2 and'aromatic compounds to said first extraction zone. y

7. A process for reiiningpetroleum oils that contain objectionable amounts of organic sulfur compounds and of aromatic compounds which process comprises contacting in a rst extraction step said oil with from about 0.5 to about 5 moles of a promoter selected from the class of Friedel- Crafts halides consistingof BFS, AlCla, FeCla, TiCli, HgClz, BCla and ZnCl2 and a solvent containing from about 15 to about 50 volume per cent of liquid SO2, based on said oil, and SO2 soluble constitutents, which solvent is derived from a second extraction step, separating a first raffinate phase from a first extract phase, contacting ina second extraction step the iirst rainate phase with from about 15 to about 200 volume per cent of liquid SO2, based on iirst raffinate oil, separating a second ra'inate phase from a second extract phase and passing the requisite amount of said second extract phase to said iirst extraction step, wherein the temperature of contacting in said extraction steps is maintained between about 0 C. and 60 C.

8. The process of claim 7 wherein the temperature of contacting is below about 20 C.

9. The process of claim 7 wherein the promoter iS BFs.

10. The process of claim 9 wherein each extraction step is conducted in a countercurrent tower and wherein the solvent to the first extraction step is introduced near the top of the tower and the BF3 is introduced intermediate the point of oil entry and the point of solvent entry.

11. The proces of claim 9 wherein the first eX- tract phase is separated to recover SO2 and BFa, the second extract phase is separated to recover SO2 and the SO2 and BFS are recycled to the process.

12. The process of claim 7 wherein the promoter is AlCls.

13. A process for reducing the organic-sulfur compound and aromatic compound content of a sulfur and aromatic containing virgin petroleum distillate boiling above the gasoline range which process comprises contacting in a rst extraction step said distillate with from about 1 to about 3 moles of BFa per mole of sulfur in said distillate and with a solvent containing liquid SO2 and SO2-soluble constituents which solvent is derived from a second extraction step and which solvent is used in such amounts that from about 15 to about 35 volume percent of liquid SO2, based on said distillate, is present in said rst extraction step, separating a iirst ranate phase from a rst extract phase, contacting the iirst raiilnate oil in a second extraction step with from about 25 to about volume percent of liquid SO2, based on said iirst rainate, separating a second raffinate phase from a second extract phase, passing the requisite amount of said second extract phase to said first extraction step to supply said solvent therefor, wherein said extraction steps being conducted at a temperature not higher than about 20 C. and wherein the time of contact in each extraction step is from about 5 minutes to 1 hour, removing the SO2 and BF; from said first extract phase to recover a fraction consisting essentially of organic sulfur compounds, removing the SO2 from the second rafiinate phase to recover an oil low in both aromatics and organic-sulfur compounds, removing the SO2 from the second extract phase to recover an oil consisting of aromatic compounds and a minor amount of organic-sulfur compounds gef-1,646

recycling the SO; and @F3 to the extraction steps.

414. A process for refining a hydrocarbon oil which contains both aromatic and organic sulcompounds which process comprises contactiiig il; a rst extractionvzone said oil with a lsol- Yefnt, containing liquid SO2 and added aromatic cgrfipourids, and an effective amount of a prometer for vincreasing the solubility of saidv Qrgvaiesulfiir compounds in liquid S92, which promoter is selected from the class of Friedel- Gaft's lia'lijies consisting of BFS, A1013, FeCls, Tick., ligen ser and znclz, wherein the aiouiii; of liquid) SO2 usel js suicient to form igwo phases, separat-ing a first; extract phase consist;- lg @sen 1y of iqillid S02r Substantially all the ailsi, PMPO??? and lfh in Organic-Suf'ur Com- Pmmds from e @ist remate phase. wntaciine 'said raiiiat phase in a seorid extra @se with .liquid S62, in the absence of ,added @www '0f prometer. to fbrm a- Sermd extract References .Cited in the file of this partent .STATES PATENTS 

1. A PROCESS FOR REFINING A HYDROCARBON OIL WHICH CONTAINS BOTH AROMATIC AND SULFURE COMPOUNDS, WHICH PROCESS COMPRISES EXTRACTING SAID OIL IN A FIRST EXTRACTION ZONE WITH AN AROMATIC COMPOUND-LIQUID SO2 SOLVENT AND AN EFFECTIVE AMOUNT OF AN ADDED PROMOTER SELECTED FROM THE CLASS OF FRIEDEL-CRAFTS HALIDES CONSISTING OF BF3, ALC3, FECL3, TICL4, HGCL2, BCL3 AND ZNCL2, AND THE AMOUNT OF LIQUID SO2 BEING SUFFICIENT TO EFFECT FORMATION OF SEPARATE PHASE IN THE PRESENCE OF THE OIL AND PROMOTER WHEREBY A FIRST EXTRACT PHASE WHICH CONTAINS LIQUID SO2, PROMOTER AND PREDOMINANTLY ORGANIC-SULFUR COMPOUNDS AND A FIRST RAFFINATE PHASE ARE OBTAINED, EXTRACTING SAID FIRST RAFFINATE PHASE IN A SECOND EXTRACTION ZONE WITH LIQUID SO2, IN THE ABSENCE OF ANY SUBSTANTIAL AMOUNT OF SAID PROMOTER, TO OBTAIN A SECOND RAFFINATE PHASE SUBSTANTIALLY REDUCED IN BOTH AROMATIC AND ORGANIC-SULFUR COMPOUND CONTENT AND A SECOND EXTRACT PHASE WHICH CONTAINS LIQUID SO2, PREDOMINANTLY AROMATIC HYDROCARBONS AND A MINOR AMOUNT OF ORGANIC-SULFUR COMPOUNDS, REMOVING SO2 AND PROMOTER FROM SAID FIRST AND SECOND EXTRACT PHASES RESPECTIVELY AND REMOVING SO2 FROM SAID SECOND RAFFINATE PAHSE. 